I'm a lawyer that does this stuff. When most people die and the heirs reasonably split the dead peoples stuff.

The problem is when they do fight about the money it quickly becomes less about what should properly happen and more about whatever family issue has existed between the fighting heirs/beneficiaries for decades. It can that one last chance for revenge because sibling a got the Christmas present that sibling b really wanted when they were children in 1968.

To be honest the most common dispute about this stuff is when one heir believes they're entitled to more because they took care of the deceased at the end of their life. Sometimes they're right to have that entitlement and it's supported by the planning docs, sometimes they're not. Planning for that and explicitly explaining your desires if this is your situation can be really helpful at preventing a fight.